Error installing RCall and Feather

I am getting the following error when trying to add the RCall package. Got the same error when I tried installing Feather before RCall. I don’t understand what is wrong. Would appreciate if someone can help.

Thank you.

Stacktrace

Pkg.add("RCall")
 Resolving package versions...
ERROR: MethodError: Cannot `convert` an object of type Nothing to an object of type String
Closest candidates are:
  convert(::Type{T<:AbstractString}, ::T<:AbstractString) where T<:AbstractString at strings/basic.jl:208
  convert(::Type{T<:AbstractString}, ::AbstractString) where T<:AbstractString at strings/basic.jl:209
  convert(::Type{T}, ::T) where T at essentials.jl:167
Stacktrace:
 [1] setindex!(::Dict{Base.UUID,String}, ::Nothing, ::Base.UUID) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [2] deps_graph(::Pkg.Types.Context, ::Dict{Base.UUID,String}, ::Dict{Base.UUID,Pkg.Types.VersionSpec}, ::Dict{Base.UUID,Pkg.Types.Fixed}) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [3] resolve_versions!(::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}, ::Nothing) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [4] #add_or_develop#63(::Array{Base.UUID,1}, ::Symbol, ::typeof(Pkg.Operations.add_or_develop), ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [5] #add_or_develop#17(::Symbol, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Pkg.API.add_or_develop), ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [6] #add_or_develop#12(::Base.Iterators.Pairs{Symbol,Symbol,Tuple{Symbol},NamedTuple{(:mode,),Tuple{Symbol}}}, ::typeof(Pkg.API.add_or_develop), ::String) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [7] add(::String) at /Applications/JuliaPro-1.2.0-1.app/Contents/Resources/julia/Contents/Resources/julia/lib/julia/sys.dylib:?
 [8] top-level scope at REPL[3]:1

It appears that you are using JuliaPro-1.2.0. Have you tried with the standard Julia distribution from https://julialang.org/downloads ?

Yes, it worked with the standard (stable) version 1.0.5. Thanks.